Patterned glass layers in electronic devices

ABSTRACT

An electronic device may include electrical components and other components mounted within an interior of a housing. The device may have a display on a front face of the device and may have a glass layer that forms part of the housing on a rear face of the device. The glass layer may be provided with regions having different appearances. The regions may be textured, may have coatings such as thin-film interference filter coatings formed from stacks of dielectric material having alternating indices of refraction, may have metal coating layers, and/or may have ink coating layers. Textured surfaces may be formed on thin glass layers and polymer films that are coupled to the glass layer. A glass layer may be formed from a pair of coupled glass layers. The coupled layers may have one or more recesses or other structures to visually distinguish different regions of the glass layer.

This application claims the benefit of provisional patent applicationNo. 62/539,454, filed Jul. 31, 2017, which is hereby incorporated byreference herein in its entirety.

BACKGROUND

This relates generally to electronic devices, and, more particularly, toforming visually distinguishable regions in glass structures inelectronic devices.

Electronic devices such as cellular telephones, computers, watches, andother devices may contain glass structures. For example, electronicdevices may have displays in which an array of pixels is covered with atransparent layer of glass. In some devices, a rear housing wall may becovered with a layer of glass. A decorative layer may be applied to thelayer of glass to help improve the appearance of the rear housing wall.

SUMMARY

An electronic device may include electrical components and othercomponents mounted within an interior of a housing. The device may havea display on a front face of the device and may have a glass layer thatforms a rear housing wall on an opposing rear face of the device.

The rear housing wall may be provided with regions having differentappearances. The regions may be selectively textured, may be selectivelyprovided with coatings such as thin-film interference filter coatingsformed from stacks of dielectric material having alternating indices ofrefraction, metal coating layers, and/or ink coating layers, and/or maybe provided with other structures that visually distinguish regions fromeach other.

A region of the rear housing wall may have a matte appearance formedfrom a textured surface. Textured surfaces may be formed directly on theglass layer and/or textured surfaces may be formed on thin glass layersand polymer films that are coupled to the glass layer.

A glass layer may be formed form a pair of coupled glass layers. Thecoupled layers may have one or more recesses or other structures tovisually distinguish different regions of the glass layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device inaccordance with an embodiment.

FIG. 2 is a cross-sectional side view of an illustrative electronicdevice in accordance with an embodiment.

FIG. 3 is a rear view of an illustrative electronic device in accordancewith an embodiment.

FIG. 4 is a cross-sectional side view of an illustrative glass layerwith a textured region and a smooth region overlapped by a coating on anouter surface of the glass layer in accordance with an embodiment.

FIG. 5 is a cross-sectional side view of an illustrative glass layerwith an outer surface having a textured region and a smooth region andhaving an inner surface with a coating that overlaps the smooth regionin accordance with an embodiment.

FIG. 6 is a cross-sectional side view of an illustrative glass layerwith an inner film with textured regions in accordance with anembodiment.

FIG. 7 is a cross-sectional side view of an illustrative glass layercovered with a textured thin glass layer and multiple coatingsinterposed between the thin glass layer and an outer surface of theglass layer in accordance with an embodiment.

FIG. 8 is a cross-sectional side view of an illustrative glass layerwith an outer surface covered with a layer such as a thin glass layerand an interposed coating in accordance with an embodiment.

FIG. 9 is a cross-sectional side view of an illustrative glass layercoated with multiple selectively textured layers in accordance with anembodiment.

FIG. 10 is a cross-sectional side view of an illustrative glass layerwith a textured coated film attached to the glass layer with aninterposed layer of adhesive in accordance with an embodiment.

FIG. 11 is a cross-sectional side view of an illustrative glass layerwith textured regions formed directly on an outer surface of the glassin accordance with an embodiment.

FIG. 12 is a cross-sectional side view of an illustrative glass layerwith textured regions formed directly on an inner surface of the glassin accordance with an embodiment.

FIG. 13 is a cross-sectional side view of an illustrative glass layerhaving a textured surface and having a recess with a taperedcross-sectional profile in accordance with an embodiment.

FIG. 14 is a cross-sectional side view of an illustrative glass layerformed from a pair of coupled sublayers having overlapping recesses thatdefine a cavity within the glass layer in accordance with an embodiment.

FIG. 15 is a cross-sectional side view of an illustrative glass layerwith visible internal structures such as laser-damaged regions embeddedwithin the glass layer in accordance with an embodiment.

FIG. 16 is a cross-sectional side view of an illustrative glass layerwith a coating having particles such as glass particles in accordancewith an embodiment.

DETAILED DESCRIPTION

Electronic devices and other items may be provided with structures thatare formed from transparent materials. For example, an electronic devicemay include a display. The display may have an array of pixels fordisplaying images for a user. To protect the pixel array from damage,the display may be covered with a layer of transparent material thatserves as a display cover layer. The transparent material may beceramic, polymer, crystalline material such as sapphire, or othersuitable transparent material. Configurations in which such layers areformed from glass are sometimes described herein as an example. Portionsof electronic devices such as optical windows, buttons, housing walls(e.g., rear housing walls), and other structures other than displaycover layers may also be formed from ceramic, polymer, crystallinematerial such as sapphire, and/or glass and may be clear or may becolored. For example, the rear face of an electronic device may becovered with a layer of glass that forms a rear housing wall.

It may be desirable to locally and/or globally modify the appearance ofa layer of glass (or other layer of material) in an electronic device.For example, it may be desirable to create attractive trim around adisplay, around the periphery of a camera window or button, or othersuitable location. In some arrangements it may be desirable toselectively modify the appearance of a glass layer or other structure toform text, graphical patterns such as icons, logos, and/or otherpatterns visible to a user.

When creating structures such as these, there is a potential forunattractive features to develop on the glass layer. For example, ifcare is not taken, undesired shadowing may occur or surfaces may appearto sparkle excessively.

These concerns can be addressed by forming visually distinguishableareas on the glass layer (e.g., visually distinguishable regions forforming logos, text, etc.) using textured areas, neutrally colored ornon-neutrally colored reflective coatings formed from a stack ofalternating high and low index-of-refraction dielectric layers or otherthin-film interference filter coatings (sometimes called dichroic layersor decoration layers), ink layers, adhesive layers, and/or otherstructures that selectively and/or globally impart visible changes toglass layers and other layers in an electronic device.

An illustrative electronic device of the type that may include glassstructures is shown in FIG. 1. Electronic device 10 may be a computingdevice such as a laptop computer, a computer monitor containing anembedded computer, a tablet computer, a cellular telephone, a mediaplayer, or other handheld or portable electronic device, a smallerdevice such as a wristwatch device (e.g., a watch with a wrist strap), apendant device, a headphone or earpiece device, a device embedded ineyeglasses or other equipment worn on a user's head, or other wearableor miniature device, a television, a computer display that does notcontain an embedded computer, a gaming device, a navigation device, anembedded system such as a system in which electronic equipment with adisplay is mounted in a kiosk or automobile, equipment that implementsthe functionality of two or more of these devices, or other electronicequipment. In the illustrative configuration of FIG. 1, device 10 is aportable device such as a cellular telephone, media player, tabletcomputer, wrist device, or other portable computing device. Otherconfigurations may be used for device 10 if desired. The example of FIG.1 is merely illustrative.

In the example of FIG. 1, device 10 includes a display such as display14 mounted in housing 12. Housing 12, which may sometimes be referred toas an enclosure or case, may be formed of plastic, glass, ceramics,fiber composites, metal (e.g., stainless steel, aluminum, titanium,gold, etc.), other suitable materials, or a combination of any two ormore of these materials. Housing 12 may be formed using a unibodyconfiguration in which some or all of housing 12 is machined or moldedas a single structure or may be formed using multiple structures (e.g.,an internal frame structure, one or more structures that form exteriorhousing surfaces, etc.).

Display 14 may be a touch screen display that incorporates a layer ofconductive capacitive touch sensor electrodes or other touch sensorcomponents (e.g., resistive touch sensor components, acoustic touchsensor components, force-based touch sensor components, light-basedtouch sensor components, etc.) or may be a display that is nottouch-sensitive. Capacitive touch screen electrodes may be formed froman array of indium tin oxide pads or other transparent conductivestructures.

Display 14 may include an array of pixels formed from liquid crystaldisplay (LCD) components, an array of electrophoretic pixels, an arrayof plasma pixels, an array of organic light-emitting diode pixels orother light-emitting diodes, an array of electrowetting pixels, orpixels based on other display technologies.

Display 14 may include one or more layers of glass. For example, theoutermost layer of display 14, which may sometimes be referred to as adisplay cover layer, may be formed from a hard transparent material suchas glass to help protect display 14 from damage. Other portions ofdevice 10 such as portions of housing 12 and/or other structures mayalso be formed from glass. For example, walls in housing 12 such as arear housing wall may be formed from glass.

FIG. 2 is a cross-sectional side view of an illustrative device thatcontains glass structures such as device 10 of FIG. 1. As shown in FIG.2, device 10 may have opposing front and rear faces. Display 14 may beformed on the front face of device 10. Housing 12 may have a rearhousing wall formed from layer 24 on the opposing rear face of device10. Portions of housing 12 may also form sidewalls for device 10. Thesesidewall portions of housing 12 may be formed from a material such metal(as an example).

Display 14 may include display cover layer 16 (e.g., a layer of glass)and display module 18 (e.g., display layers that form an array of pixelsthat present images for a user on the front face of device 10). Displaymodule 18 may be a liquid crystal display structure, an organiclight-emitting diode display structure, or other suitable display.During operation, module 18 may present images that are viewable throughdisplay cover layer 16. The rear of the housing for device 10 may beformed from a glass structure (e.g., layer 24 may be a glass layer). Thethickness of layer 24 may be 0.2-5 mm, at least 0.05 mm, at least 0.1mm, at least 0.2 mm, at least 0.5 mm, at least 0.75 mm, less than 1 mm,less than 2 mm, or other suitable thickness. If desired, a metal plateor other strengthening structures may be laminated to the inner surfaceof layer 24 to enhance strength. Internal components in device 10 suchas components 22 (e.g., electrical components such as integratedcircuits, sensors, etc.) may be mounted on one or more substrates suchas printed circuit 20.

Inactive border areas in layer 16 and portions of other glass structuresin device 10 such as some or all of glass layer 24 may be covered withcoatings and other structures. In some arrangements, a coating may beused primarily to block light (e.g., to hide internal device structuresfrom view). For example, a coating may be formed on the inner surface oflayer 24 to hide internal components from view from a user such asviewer 26 who is viewing device 10 in direction 28. In otherarrangements, a patterned coating may be used to form text, logos, trim,and/or other visible patterns. Coatings that are unpatterned and thatcoat all of glass layer 24 may also be used to block internal structuresfrom view and/or to provide device 10 with a desired appearance.Patterned coatings may create visible elements and may also blockinternal structures from view.

Coatings for glass structures in device 10 may be black or other neutralcolors or may have non-black (non-neutral) colors (e.g., blue, red,yellow, gold, rose gold, red-violet, pink, etc.). In someconfigurations, some or all of the coatings for glass structures indevice 10 may be shiny (e.g., exhibiting a mirror-like reflectivesurface with a reflectance of at least 50%, at less 80%, at least 95%,less than 99.99%, or other suitable reflectance). Textured features mayalso be formed.

If desired, a coating may include one or more layers that definetextured regions on a layer such as glass layer 24 that are interspersedwith smooth and shiny regions that are not textured. As an example, alogo may be formed form a shiny region and may be surrounded by a mattetextured region. Textured and shiny regions may be formed from texturedand/or reflective surfaces on glass layer 24 and/or on one or morelayers coupled to glass layer 24. For example, textured and/or shinyregions may be formed from textured and/or shiny films that are adheredto glass layer 24. Textured and shiny regions may also be defined bytexturing selected portions of glass layer 24 directly.

Coatings on glass layer 24 and/or other glass structures in device 10may be formed from metals, semiconductors, and/or dielectrics.Dielectric materials for the coatings may include organic materials suchas polymer layers and/or inorganic materials such as oxide layers,nitride layers, and/or other inorganic dielectric materials. Inarrangements in which a shiny surface is desired, a metal coating with ahigh reflectivity or a thin-film interference filter with dielectriclayers (e.g., a stack of dielectric layers of alternating higher andlower refractive index values) may be configured to serve as a mirrorcoating (reflective coating). Ink coatings may also be incorporated ontothe glass structures.

FIG. 3 is a top view of an illustrative configuration for the rear faceof device 10 in which one region (region 24-1) has a first appearance(textured, shiny, a particular color, etc.) and has a first shape (e.g.,text, a logo, a trim pattern, or other patterned shape) and in whichanother region (background region 24-2 in this example) has a secondappearance (e.g., textured, shiny, a particular color, etc.). In orderto ensure that region 24-1 is visible to a user of device 10, theappearances of regions 24-1 and 24-2 may contrast with each other. Forexample, in a scenario in which region 24-1 is reflective (e.g., inwhich region 24-1 is a shiny silver or gold region associated with alogo, text, etc.), region 24-2 may have a matte finish.

Glass layer 24 may have any suitable number of separately patternedregions such as regions 24-1 and 24-2, each of which may potentiallyhave a different separate appearance. Configurations in which glasslayer 24 has one or more patterned layers that provide textured andshiny regions may sometimes be described herein as an example. Theregions of device 10 that have different appearances may be formed byselectively patterning glass layer 24 and associated coatings, films,and other structures. For example, these regions may be selectivelyformed by depositing coatings using physical vapor deposition, chemicalvapor deposition, or other deposition techniques followed byphotolithography and etching, using shadow-masking or other selectivedeposition techniques such as printing techniques, by using selectivesurface treatment such as selective laser treatment, selectiveroughening or polishing using mechanical or chemical-mechanicalpolishing equipment, selective treatment with machining equipment,sand-blasting equipment or blasting equipment using other particles, byroughening or otherwise processing the surfaces of polymer films usingembossing tools, presses, and/or by using other equipment forselectively processing particular areas of coatings, films, and/orsurfaces (e.g., glass layer surfaces).

Textured surfaces in layer 24 and/or in coatings, films, and/or otherlayers coupled to layer 24 may provide a matte finish. These texturedsurfaces may have protruding surface structures that are 100 s of nm to1 micron in height (e.g., at least 100 nm, at least 500 nm, less than 5microns, less than 1 micron). Such textured surfaces may have an RMSsurface roughness of 100 nm to 2 microns or other suitable value thatprovides a desired appearance (e.g., a matte appearance). Smoothsurfaces (e.g., polished surfaces or other smooth surfaces) may haveprotruding surface features that are less than 5 nm in height, surfaceswith features that are less than 50 nm in height, etc.). Such smoothsurfaces may have an RMS surface roughness of less the RMS surfaceroughness of the textured surfaces (e.g., an RMS surface roughness ofless than 25 nm or other suitable value that provides a desiredappearance such as a smooth potentially reflective appearance). Ifdesired, regions of the rear housing wall of device 10 or otherglass-layer structures may have other roughness values (e.g., valuesintermediate to those associated with strongly textured matte finishesand smooth reflective finishes). The use of textured and smooth surfacesto form visually distinct regions of glass layer 24 is merelyillustrative.

FIGS. 4-16 set forth various examples of patterned regions on astructure in device 10 such as a rear housing wall (e.g., glass layer24) that have potentially different visual appearances. These regionsmay be used in forming logos, text, trim, and/or other patterns. Theremay be any suitable number of patterned regions on layer 24 and theselayers may include textured backgrounds and smooth backgrounds, texturedforegrounds and smooth backgrounds, background and foreground elementsof different colors, reflectivity values, etc. Coatings may be providedon the outer surface of these illustrative patterned regions (e.g.,antismudge coatings, antiscratch coatings, etc.) or, if desired, theseexternal coating layers may be omitted and/or incorporated into thecoatings, films, and surfaces forming layer 24. The examples of FIGS.4-16 are merely illustrative.

FIG. 4 is a cross-sectional side view of glass layer 24 in anillustrative configuration in which the outer surface of layer 24 has atextured region and a coated region such as a smooth shiny region. Thetextured region is visually distinguishable from the smooth regionbecause the surface roughness of the textured region is larger than thatof the smooth region and therefore may provide the textured region witha matte appearance. Glass layer 24 may have opposing inner and outersurfaces such as inner surface 32 and outer surface 30. Inner surface 32may face internal device components such as components 22 of FIG. 1 inthe interior of housing 12 and device 10. Outer surface 30 may face auser of device 10 such as viewer 42 who is viewing device 10 indirection 44 from the exterior of device 10.

In the example of FIG. 4, inner surface 32 is smooth and is coated byinner coating layer 34. Coating layer 34 may be a global layer thatcovers all of the inner surface of layer 24 (as an example). Outercoating layer 36 may be formed on region 40 of outer surface 30. Region38 of outer surface 30 may be textured and may, if desired, surroundregion 40. Coatings 36 and 34 may include one or more sublayers (see,e.g., illustrative sublayers 46 of coating 34) or may each be formed ofonly a single layer of material.

Coatings 36 and 34 may be shiny. For example, a stack of multipledielectric sublayers in coating 36 and/or 34 may have alternating indexof refraction values to form a thin-film interference filter or coating36 and/or coating 34 may include a reflective material such as metal.The texture of outer surface 30 in region 38 may provide glass layer 24with a pleasing feeling to the touch. Coating 36 in region 40, which maybe a physical vapor deposition coating deposited through a shadow maskor other patterned layer, may be shaped to form text, a logo, or othervisual element and may have a different appearance than textured outersurface 30 in region 38. Coating 34 may help hide internal componentsfrom view by blocking light transmission into the interior of device 10.If desired, coating 34 may be formed from an opaque material such asneutrally colored (white, black, or gray) or non-neutrally colored (red,blue, yellow, etc.) ink.

In the illustrative configuration of FIG. 5, coating 36 in region 40 hasbeen formed on inner surface 32 of glass layer 24. Outer surface 30 issmooth in region 40 and textured in region 38. This approach protectscoating 36 under glass layer 24.

FIG. 6 is a cross-sectional side view of an illustrative glass layer towhich a layer of film with textured regions has been attached. As shownin FIG. 6, film 48 (e.g., a flexible polymer sheet) may have a smoothsurface that is attached to inner surface 32 of glass layer 24. Film 48may be attached directly to surface 32 or may be attached to surface 32with an intervening layer of adhesive. Film 48 may have an inner surfacethat is textured in region 38 and that is smooth in region 40, so thatregions 38 and 40 have respective matte and shiny appearances. Film 48may be covered with polymer layer 50. Polymer layer 50 may have a lowerindex of refraction than film 48 and may be covered with coating 52.Coating 52 may be formed from ink or a shiny material such as metal. Ifdesired, coating 52 may be a shiny coating formed from a thin-filminterference filter with high reflectively.

In the example of FIG. 7, layer 54 may be a polymer film or may be athin glass layer that is thinner than glass layer 24 (e.g., at least 3times thinner, at least 7 times thinner, at least 10 times thinner, atleast 20 times thinner, etc.). The use of glass as an outer layer on topof glass layer 24 may help reduce scratches. In configurations in whichglass is used, the thickness of layer 54 may be relatively thin toenhance the appearance of the logo or other pattern formed by region 40.Layer 54 may, if desired, be a thin glass layer with at thickness of20-250 microns, at least 30 microns, at least 100 microns, at least 150microns, less than 200 microns, less than 500 microns, or less than 800microns. Thin glass layer 54 may have an outer surface that is texturedin region 38 to provide region 38 with a matte appearance that is smoothin region 40 or textured region 38 may be formed from a textured surfaceon the inner surface of layer 54.

As shown in FIG. 7, the inner surface of layer 54 may be selectivelycoated with first coating layer 56 in region 40 (e.g., a patternedcoating layer). A second coating layer such as blanket coating layer 58may be used to cover coating layer 56. Coatings 56 and 58 may provide anattractive appearance (e.g., a shiny appearance with a desired color,reflectivity, etc.). Coatings 56 and 58 may be formed from dielectricthin-film interference filters (e.g., stacks of alternating high and lowindex-of-refraction materials), may be formed from metal, and/or may beformed from other materials (e.g., ink). Because coating layer 56 ispresent only in region 40 and not in region 38, the presence of coatinglayer 56 will help to visually distinguish regions 38 and 40. If desiredcoating 56 may be omitted and/or coating 58 may be omitted or coating 58may be selectively omitted from region 40 and not region 38. Opticallyclear adhesive 60 may be used in attaching film 54 and coatings 56 and58 to outer surface 30 of layer 24. If desired, coating 56 (e.g., athin-film interference filter, metal coating layer, and/or ink layer)may be formed on inner surface 32 of glass layer 24 instead of on theinner surface of film 54, as illustrated by coating 56′. In otherconfigurations, both coatings 56 and 56′ may be used.

FIG. 8 is a cross-sectional side view of glass layer 24 in anillustrative configuration in which a thin glass layer with a texturedinner surface has been coupled to outer surface 30. As shown in FIG. 8,thin glass layer 66 (e.g., a glass layer with at thickness of at least30 microns, at least 100 microns, at least 150 microns, less than 200microns, less than 500 microns, or less than 800 microns that is atleast 3 times thinner, 7 times thinner, 10 times thinner, 20 timesthinner, etc. than layer 24) may have a textured inner surface in region38 to provide region 38 with a matte appearance. The inner surface ofthin glass layer 66 may be smooth in region 40. Coating layer 64 (e.g.,a dielectric thin-film interference coating, a metal thin-film coating,or other material such as ink) may be formed on the inner surface oflayer 66. If desired, other patterned coatings such as coating 64 may beprovided, as described in connection with the multiple coatings on layer54 of FIG. 7 (e.g., only in region 38, only in region 40, or overlappingboth regions 38 and 40). Optically clear adhesive 62 may be used toattach layer 66 and coating layer 64 to outer surface 30 of layer 24.

If desired, chemical strengthening may be used to strengthen thin-glasslayers such as layer 54 of FIG. 7 or layer 66 of FIG. 8. In otherconfigurations, thin-glass layers such as layer 54 and layer 66 may bereplaced by a layer of polymer with textured regions and smooth regions.

In the example of FIG. 9, layer 72 has an outer surface with texture inregion 38. The inner surface of layer 72 may be textured in region 38and region 38′. As a result, textured region 38 will have an appearancethat is more matte than the appearance of textured region 38′. Layer 72may be formed from a thin glass layer (see, e.g., layer 54 of FIG. 7 andlayer 66 of FIG. 8) or a sheet of polymer. Coating layer 70 may beformed on the inner surface of layer 72 and optically clear adhesivelayer 68 may be used in attaching layer 72 and coating 70 on layer 72 toouter surface 30. Coating layer 70 may be a thin-film interferencefilter, metal layer, or ink layer. There is no texture on layer 72 orcoating 70 in region 40, so region 40 will not have a matte appearance.Because region 38 and region 38′ have different appearances, regions 38and/or 38′ may be provided with the shapes of text, logos, trimpatterns, and/or other patterns and may be visually distinguished byviewer 42.

Another illustrative arrangement is shown in FIG. 10. As shown in FIG.10, inner surface 32 of glass layer 24 may be textured to provide anoverall matte appearance to layer 24. Coating layer 74 (e.g., athin-film interference filter coating, metal coating, and/or inkcoating) may be used to help block internal components from view by user42. Layer 80 (e.g., a polymer film or a thin glass layer) may have anouter surface that is textured in region 38 to enhance the matteappearance of glass layer 24 in region 38. In region 40, the outersurface of layer 80 may be smooth. Coating layer 78 may be selectivelyformed in region 38 on the inner surface of layer 80 to adjust color,reflectivity, and/or other optical characteristics in region 38 relativeto region 40. Optically clear adhesive 76 may be used in attaching layer80 to outer surface 30 of layer 24.

In the illustrative configuration of FIGS. 11 and 12, a first texture isformed in region 38 and a second texture (e.g., a texture for a logo,text, or other pattern) or no texture is formed in region 40. Coatinglayer 82 (e.g., a thin-film interference filter coating, metal coating,and/or ink coating) may be formed on inner surface 32. In the example ofFIG. 11, outer surface 30 of glass layer 24 is textured (e.g., with afirst texture in region 38 and a different second texture or no texturein region 40). In the example of FIG. 12, inner surface 32 of glasslayer 24 is selectively textured in this way.

FIG. 13 shows how inner surface 32 of glass layer 24 may have a recess(e.g., a recess with sloped sidewalls, vertical sidewalls, or othersidewall profile). Protruding layer 88 (e.g., a glass or polymer layerwith a thickness T of about 50-150 microns, at least 75 microns, fewerthan 500 microns, etc.) may have a protrusion that is placed in therecess in inner surface 32 and that has a shape that mates with thisrecess. An optional layer such as layer 90 (e.g., a thin-filminterference filter coating, metal coating, and/or ink coating and/or alayer of adhesive) may be interposed between layer 88 and layer 24.

In the example of FIG. 14, glass layer 24 has been formed from matingfirst and second layers such as outer layer 24A and inner layer 24B.Inner surface 32′ of outer layer 24A and/or outer surface 30′ of innerlayer 24B may be provided with recesses, protrusions, and/or othernon-planar portions to create visual contrast between regions 38 and 40.For example, inner surface 32′ may have recess 90 and outer surface 30′may have a fully or partly overlapping recess such as recess 92 (e.g., amating recess). The inner surfaces of recesses 90 and 92 may, ifdesired, be provided with respective coating layers 94 and 96 (e.g.,thin-film interference filter coatings, metal coatings, and/or inkcoatings). Recesses 90 and 92 may be filled with air, a liquid, apolymer, a glass insert or an insert formed from other material, and/orother material. Outer layer 24A and inner layer 24B may be coupled usingadhesive 98. In some configurations, recess 90 or recess 92 may beomitted. Glass layer 24 may also be formed only from layer 24A and notlayer 24B, if desired.

If desired, laser processing techniques may be used to form visiblestructures on glass layer 24. For example, high power laser beams may befocused into interior portions of glass layer 24. This may createlaser-damaged regions that are embedded within layer 24, as shown bylaser-damaged portions 100 of FIG. 15. Laser processing to form thesevisible laser-processed structures may take place in region 40 but notregion 38 (or vice versa) to provide regions 38 and 40 of glass layer 24with a visually distinguishable appearance. Optional coating layer 100(e.g., a thin-film interference filter coating, metal coating, and/orink coating) may be formed on inner surface 32 of layer 24.

As shown in FIG. 16, inner surface 32 of glass layer 24 may be coatedwith a polymer layer such as layer 106. Layer 106 may contain particlessuch as particles 108. Particles 108 may have a different refractiveindex than the polymer binder that makes up layer 106 and may have adiameter that is sufficient to give rise to light ray reflection.Particles 108 may, for example, be glass particles having diameters of20-100 microns, at least 10 microns, at least 30 microns, fewer than 200microns, etc. and may provide glass layer 24 with a pearlescentappearance.

If desired, one or more of the polymer layers of FIGS. 4-16 coupled toglass layer 24 may be formed from glass rather than polymer and/or oneor more of the glass layers coupled to glass layer 24 may optionally beformed from a polymer coating or polymer film. Glass layer 24 may bereplaced with a polymer layer or a layer of other material (sapphire orother crystalline material, ceramic, etc.). The illustrative structuresof FIGS. 4-16 may be formed on a glass layer 24 that forms part of arear housing wall, a window structure for an optical component, adisplay cover layer, a button member, a keyboard key, a trackpadsurface, or any other suitable structure in device 10. The examples ofFIGS. 4-16 are merely illustrative and the coatings, glass layers,films, textures, and other structures of these examples may be usedtogether, if desired (e.g., by stacking the layers of one configurationon top of those of another, in laterally spacing the structures fromdifferent configurations across a common glass layer, etc.).

The foregoing is merely illustrative and various modifications can bemade to the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. An electronic device having opposing front andrear faces and an interior, comprising: a display on the front face; afirst glass layer that is separate from the display and that forms ahousing wall on the rear face, wherein the first glass layer has aninner surface facing the interior and an opposing outer surface; asecond glass layer that is separate from the display, that is thinnerthan the first glass layer, and that has an outer surface and anopposing inner surface that faces the outer surface of the first glasslayer; and a layer of adhesive between the first and second glass layersthat couples the second glass layer to the first glass layer.
 2. Theelectronic device defined in claim 1 wherein the second glass layer hasa smooth region and has a textured region with a larger surfaceroughness than the smooth region.
 3. The electronic device defined inclaim 2 wherein the textured region is formed on the outer surface ofthe second glass layer.
 4. The electronic device defined in claim 2wherein the textured region is formed on the inner surface of the secondglass layer.
 5. The electronic device defined in claim 2 furthercomprising: a first thin-film interference filter coating on the secondglass layer that overlaps the smooth region and does not overlap thetextured region; and a second thin-film interference filter coating onthe second glass layer that overlaps the smooth region and the texturedregion.
 6. The electronic device defined in claim 2 further comprising:a thin-film interference filter coating on the inner surface of thefirst glass layer that overlaps the smooth region and does not overlapthe textured region.
 7. The electronic device defined in claim 1 whereinthe second glass layer has first and second regions with differentrespective surface roughness values and wherein the electronic devicefurther comprises a coating on the second glass layer that overlaps thefirst region.
 8. The electronic device defined in claim 7 wherein thefirst region is a smooth region, wherein the second region is a texturedregion, and wherein the coating comprises a thin-film interferencecoating having a stack of dielectric layers.
 9. The electronic devicedefined in claim 1 further comprising a coating on the inner surface ofthe second glass layer.
 10. The electronic device defined in claim 9wherein the coating is a thin-film interference filter coating.
 11. Theelectronic device defined in claim 10 wherein the second glass layer hasa smooth region and has a textured region with a larger surfaceroughness than the smooth region.
 12. The electronic device defined inclaim 11 wherein the thin-film interference filter coating overlaps thesmooth region and does not overlap the textured region.
 13. Theelectronic device defined in claim 11 wherein the thin-film interferencefilter coating overlaps the smooth region and the textured region. 14.An electronic device having opposing front and rear faces and aninterior, comprising: a display on the front face; a first glass layerforming a housing wall on the rear face, wherein the first glass layerhas an inner surface facing the interior and an opposing outer surface;and a second glass layer that is thinner than the first glass layer,wherein the second glass layer has an outer surface and has an opposinginner surface facing the outer surface of the first glass layer andwherein the inner surface of the second layer of glass has a smoothregion and has a textured region with a larger surface roughness thanthe smooth region.
 15. The electronic device defined in claim 14 furthercomprising a coating on the inner surface of the second glass layer. 16.The electronic device defined in claim 15 further comprising a layer ofadhesive interposed between the coating on the inner surface of thesecond glass layer and the outer surface of the first layer of glass,wherein the layer of adhesive attaches the second glass layer to thefirst glass layer.
 17. The electronic device defined in claim 16 whereinthe coating comprises a thin-film interference coating having a stack ofdielectric layers.
 18. The electronic device defined in claim 14 whereinthe second layer of glass has a thickness of 20-250 microns.
 19. Anelectronic device having opposing front and rear faces and an interior,comprising: a display on the front face; a glass layer that forms ahousing wall on the rear face, wherein the glass layer has an innersurface facing the interior and an opposing outer surface and whereinthe glass layer has a surface with a smooth region and a textured regionwith a larger surface roughness than the smooth region; and a thin-filminterference filter coating formed from a stack of dielectric layers onthe inner surface of the glass layer.
 20. The electronic device definedin claim 19 wherein the smooth and textured regions are formed fromrespective smooth and textured surfaces on the outer surface.
 21. Theelectronic device defined in claim 19 wherein the smooth and texturedregions are formed from respective smooth and textured surfaces on theinner surface.
 22. An electronic device having opposing front and rearfaces, comprising: a display on the front face; and first and secondcoupled glass layers that form a housing wall on the rear face, whereinthe first glass layer has first and second regions with differentappearances and has a recess in the first region.
 23. The electronicdevice defined in claim 22 further comprising a coating that overlapsthe first region and that does not overlap the second region.
 24. Theelectronic device defined in claim 22 further comprising a layer ofadhesive interposed between the first and second glass layers thatcouples the first and second glass layers together.
 25. The electronicdevice defined in claim 22 wherein the second glass layer has a recessthat at least partly overlaps the recess of the first glass layer.